Also on the ballot, which is part of Switzerland's direct democracy system, are controversial legal revisions that define the ways insurance companies are allowed to spy on suspected welfare cheats as well as a rightwing proposal that would give Swiss judges supremacy over world courts.
But much of the public attention has been centred on farmer Armin Capaul, who forced a national vote on safeguarding cow horns following an upstart campaign that began with few resources and no political support.
The proposal does not call for a ban on dehorning. Instead, it seeks a constitutional amendment that would create incentives for farmers to let horns grow.
Capaul has maintained that despite attention heaped on him after he defied the odds and secured the more than 100,000 signatures needed to force a national vote, he is not the story.
"It's the cow that's important, not me," the farmer, in his 70s, told AFP at his home in Perrefitte, a municipality in the heart of the Jura mountain range.
Capaul credits his cows with giving him the idea to push for Sunday's referendum.
"I always talk to my cows in the barn. They asked me if I could do something for them, if I could help them keep their horns," he said.
Polling earlier this month suggested the outcome was too close to call. Environmental and animal rights groups ultimately joined Capaul's campaign but it is opposed by the government, which argues farmers must remain free to manage their livestock as they see fit.
Opponents have underscored that dehorning is a crucial tactic allowing farmers to house animals in close proximity with less risk of injury.
Insurance company spies
Voting was also under way nationwide on a measure in which the government is seeking approval for legal revisions passed in March that give insurance companies broad leeway to spy on potential fraudsters.
Insurers in the wealthy Alpine nation had long spied on customers they suspected of making false claims, but that came to a stop following a 2016 ruling by the European Court of Human Rights which said unregulated spying
amounted to a violation of privacy.
The government insists that surveillance is necessary to curb insurance fraud and in turn keep costs low for all.
The legal amendments are expected to pass on Sunday, with latest polling suggesting the text is supported by 60 percent of voters.
But critics have argued that the measures were hastily written under pressure from insurance company lobbying and do not explicitly prohibit serious, unjustified invasions of privacy.
Legal analysts have noted that the law does not prohibit insurers, or the detectives they hire, from recording or filming someone who is on their private balcony or in their garden, provided those areas are visible from a public space.
Another measure on Sunday's ballot envisions a Switzerland where the insurance espionage debate might never have emerged, because European rights court rulings would not supersede decisions by Swiss judges.
The "Swiss Law First" proposal, backed by rightwing groups, calls for domestic law to be placed above international law.
The latest polling suggests the measure will be rejected, with the government opposed and surveys indicating voters are concerned about reputational damage to Switzerland.
President Alain Berset called it "a dangerous experiment."
"Switzerland has over 600 economic agreements that allow us to export to other countries," said Oliver Steimann, of the business lobby group economiesuisse, who is against the proposal.
If those deals are threatened because Switzerland rebukes international law, "it would threaten the country's success as an exporting nation," he told AFP.